U.S. patent number 7,456,742 [Application Number 11/467,990] was granted by the patent office on 2008-11-25 for apparatus and method for determining the position of a mobile platform.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Robert T. Cato.
United States Patent |
7,456,742 |
Cato |
November 25, 2008 |
Apparatus and method for determining the position of a mobile
platform
Abstract
A mobile platform such as a shopping cart, flatbed cart or lift
truck is provided with a plurality of radiation detectors which are
screened or limited in scope of view and which cooperate with
circuitry which can distinguish from the interaction of the sensors
with emitters the position of the platform. Position consists of
location and orientation. Each detector or sensor is screened to
limit its view to a defined portion of a sphere.
Inventors: |
Cato; Robert T. (Raleigh,
NC) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
39133599 |
Appl.
No.: |
11/467,990 |
Filed: |
August 29, 2006 |
Prior Publication Data
|
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|
|
Document
Identifier |
Publication Date |
|
US 20080061973 A1 |
Mar 13, 2008 |
|
Current U.S.
Class: |
340/568.5;
235/383; 235/385; 340/539.1; 340/539.13; 340/686.1; 340/8.1 |
Current CPC
Class: |
A47F
10/02 (20130101); B62B 3/1428 (20130101); G01S
3/781 (20130101); G01S 5/16 (20130101) |
Current International
Class: |
G08B
13/14 (20060101) |
Field of
Search: |
;340/568.5,686.1,539.1,539.13,825.36,825.49 ;235/383,385
;705/1,10,14,26 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nguyen; Hung T.
Attorney, Agent or Firm: Piche; Jason O.
Claims
What is claimed is:
1. Apparatus comprising: a mobile platform; a plurality of
radiation receivers mounted on said platform and screened to limit
the field of receptivity of each of said receivers to a defined
portion of a sphere; and circuitry operatively connected to said
receivers for distinguishing among a plurality of patterns of
reception of radiation at said receivers and identifying a position
of said platform relative to said radiation sources based upon
recognition of said patterns of reception.
2. Apparatus according to claim 1 wherein said mobile platform is a
shopping cart.
3. Apparatus according to claim 1 wherein said plurality of
radiation receivers comprises two receivers.
4. Apparatus according to claim 3 further comprising a blinder
assembly limiting the field of view of each receiver to
approximately one quarter of a sphere.
5. Apparatus according to claim 1 wherein said plurality of
receivers comprises three receivers.
6. Apparatus according to claim 5 further comprising a blinder
assembly limiting the field of view of each receiver to
approximately one sixth of a sphere.
7. Apparatus according to claim 1 wherein said plurality of
receivers comprises four receivers.
8. Apparatus according to claim 7 further comprising a blinder
assembly limiting the field of view of each receiver to
approximately one eighth of a sphere.
9. Apparatus according to claim 1 wherein differing radiation
source information received from two sensors is combined with a
known physical relationship between the sources to determine the
orientation of the mobile platform.
10. Apparatus according to claim 1 further comprising an
orientation device mounted on said mobile platform and operatively
coupled to said circuitry and cooperating therewith in determining
the orientation of said platform relative to the cardinal compass
points of as an element in identification of the position of said
platform.
11. Apparatus according to claim 10 wherein differing radiation
source information received from two sensors is combined with a
known physical relationship between the sources to validate the
orientation of the mobile platform.
12. Apparatus according to claim 1 wherein the field of view of
each of the plurality of receivers overlaps with a portion of the
field of view of another one of said plurality of receivers.
13. Method comprising: mounting a plurality of radiation receivers
on a mobile platform; screening each of the receivers to limit the
field of receptivity thereof to a defined portion of a sphere;
distinguishing among a plurality of patterns of reception of
radiation at the receivers; and identifying a position of the
platform relative to the radiation sources based upon recognition
of the patterns of reception.
14. Method according to claim 13 wherein the mounting of receivers
comprises mounting the receivers on a shopping cart.
15. Method according to claim 13 wherein the mounting of receivers
comprises mounting two receivers on a platform.
16. Method according to claim 15 wherein the screening of the
receivers comprises mounting a blinder assembly limiting the field
of view of each receiver to approximately one quarter of a
sphere.
17. Method according to claim 13 wherein the mounting of receivers
comprises mounting three receivers on a platform.
18. Method according to claim 17 wherein the screening of the
receivers comprises mounting a blinder assembly limiting the field
of view of each receiver to approximately one sixth of a
sphere.
19. Method according to claim 13 wherein the mounting of receivers
comprises mounting four receivers on a platform.
20. Method according to claim 19 wherein the screening of the
receivers comprises mounting a blinder assembly limiting the field
of view of each receiver to approximately one eighth of a
sphere.
21. Method according to claim 13 further comprising determining the
orientation of said platform relative to cardinal compass points as
an element in identification of the position of said platform.
22. Method according to claim 13 wherein differing radiation source
information received from two sensors is combined with a known
physical relationship between the sources to infer the orientation
of the mobile platform.
23. Method according to claim 13 wherein the mounting of the
receivers comprises arranging the receivers so that the fields of
view of each receivers overlaps with a portion of the field of view
of another receiver.
Description
FIELD AND BACKGROUND OF INVENTION
This invention relates to determining the position of a mobile
platform such as a cart within an environment such as a retail
establishment, a warehouse facility, or other large area.
It has been recognized in the past that the ability to determine
the position of a mobile platform such as a shopping cart within an
area traversed by the platform is useful. As here used, "position"
refers both the location, as on an X-Y coordinate grid, and
orientation, as with reference to the cardinal points of the
compass. Thus position defines both the coordinate grid location
and the "pointing" of the cart in a particular direction for next
forward movement.
An example of the usefulness of such information is found in prior
U.S. Pat. No. 4,882,724 to Vela et al. As there taught, position
information is used to provide a basis for shopper information such
as the location of products within the establishment relative to
the position of the shopping cart. Thus a shopper desiring milk can
be directed to the location within a store where milk is on
display.
A difficulty which arises with such prior apparatus and methods
lies in changes in technology which employ infra red radiation
sources and detectors to implement a location determining apparatus
and method for shopping carts. In such apparatus and methods, the
resolution available with known emitters located above the floor of
a space can become challenging. It is this challenge which the
present invention overcomes.
SUMMARY OF THE INVENTION
It is one purpose of this invention to enhance the effectiveness of
location determining apparatus and method for mobile platforms such
as shopping carts moving within a defined space such as the floor
of a warehouse or retail establishment. This purpose is realized by
providing on a cart a plurality of radiation detectors which are
screened or limited in scope of view and which cooperate with
circuitry which can distinguish from the interaction of the sensors
with emitters the position of the cart. Each detector or sensor is
screened to limit its view to a defined portion of a sphere.
BRIEF DESCRIPTION OF DRAWINGS
Some of the purposes of the invention having been stated, others
will appear as the description proceeds, when taken in connection
with the accompanying drawings, in which:
FIG. 1 is a perspective view of a mobile platform, in the form of a
shopping cart, equipped with a plurality of radiation receivers as
contemplated by this invention;
FIG. 2 is an enlarged scale perspective view of a pair of receivers
as illustrated in FIG. 1, showing in phantom lines the positioning
of the screen or blinder which limits the field of view of the
receivers;
FIG. 3 is a simplified vertical elevation view showing the
relationships between an overhead IR emitter and the IR
illumination striking a receiver assembly of FIG. 2 when the
location of the receiver is changed in relation to the IR emitter.
FIG. 3 further illustrates configurations of two and three
receivers or sensors. Their respective screens and "footprints" as
described more fully hereinafter;
FIG. 4 is a view similar to a portion of FIG. 3 illustrating a
configuration of four receivers and their associated screen;
FIG. 5 is a view similar to portions of FIG. 3 illustrating the
"footprint" of the four receivers; and
FIG. 6 is an environmental view showing the mobile platform of FIG.
1 in one environment of use of this invention.
DETAILED DESCRIPTION OF INVENTION
While the present invention will be described more fully
hereinafter with reference to the accompanying drawings, in which a
preferred embodiment of the present invention is shown, it is to be
understood at the outset of the description which follows that
persons of skill in the appropriate arts may modify the invention
here described while still achieving the favorable results of the
invention. Accordingly, the description which follows is to be
understood as being a broad, teaching disclosure directed to
persons of skill in the appropriate arts, and not as limiting upon
the present invention.
Turning now to FIGS. 1 and 6, one form of mobile platform in
accordance with this invention is there shown as a shopping cart
10. The shopping cart 10 has mounted thereon a plurality of
radiation receivers 11 which are screened to limit the field of
receptivity of each of the receivers to a defined portion of a
sphere. While shown as a shopping cart, the mobile platform may
take other forms contemplated by this invention, such as a flatbed
cart, a lumber cart, or a fork lift truck used in various retail or
commercial environments such as an office or warehouse stores
offering quantity purchases, building materials and the like. The
environment shown in FIG. 6 for the cart 10 is that of a grocery
store or the like, where gondolas or display stands 12 are arranged
on a sales floor while an array of radiation sources or emitters 14
are disposed in a ceiling or above the gondolas. Such an
environment is known in the prior art, as for example in Vela et al
U.S. Pat. No. 4,882,724 mentioned above. Here, the emitters 14 and
receivers 11 preferably operate using infrared radiation (here also
IR). The emitters 14 may be driven in such a manner as to provide a
digitally encoded signal which specifically identifies individual
emitters or defined areas of emitters or rows or columns of
emitters, for purposes which will become more clear
hereinafter.
The basic concept of the apparatus of FIGS. 1 and 6, and the
methods of operation of the systems, is that an operator of the
cart 10 may move through the space of the area beneath the emitters
14 while circuitry associated with the receivers tracks the
position of the cart 10. Such position tracking enables and number
of desired results, from providing product prompts to a user to
providing information for customer analysis to store management to
assisting with computerized checkout schemes. The present invention
contemplates usefulness in all these manners and others not
specifically mentioned here.
In accordance with important features of this invention, the
screening of the field of view of the receivers and the circuitry
associated with the receivers cooperate in an advantageous way to
distinguish among a plurality of patterns of reception of radiation
at the receivers 11 and identify a position of the platform 10
relative to the emitters 14 based upon recognition of said patterns
of reception. FIG. 2 illustrates the positioning of a screening
partition 15 between two receivers 11 in such a way as to limit the
field of view of each of them to a defined portion of a sphere.
More particularly, where there are two receivers 11 and a single
screen or blinder 15 (FIG. 2), the view is limited to approximately
one quarter of a sphere centered on the intersection of the screen
15 with the support 16 for the receivers (about one half of the
hemisphere above the blinder 15). This limitation of the field of
view is an important characteristic of this invention and
distinguishes this invention from prior arrangements.
This effect is made more clear from FIG. 3, where the effect of
movement of the cart beneath an emitter 14 is suggested. There, it
will be seen that positioning the receivers directly beneath an
emitter (the position marked as "both") causes the two receivers of
FIGS. 1 and 2 to be equally exposed to the radiation emitted from
above. Positioning the receivers near the edge of the emitted beam
causes the one of the two receivers in FIGS. 1 and 2 to be exposed
to the radiation emitted from above while the other is not because
it is in the shadow of the blinder 15.
The IR emitter directs illumination downwardly in a cone,
illuminating a first circular area on the floor below. The elements
of the receiver 11 are mounted in a plane. The intersection of that
plane and the cone of illumination is a second circular area,
referred to herein as the "footprint" of the emitter. The circular
footprint is divided into zones, with each zone representing the
locations at which there is a particular pattern of illumination
and/or shadowing of the sensors 11 for a particular orientation of
the mobile platform. This is shown also by the portion of FIG. 3
identified as showing 2 sensors, where two receivers 11 and a
single screen 15 are shown. The circular representation shows what
occurs as the cart may be moved to the left and to the right of a
vertical position directly beneath an emitter, as either the left
or the right receiver "goes dark" or is screened from a view of the
emitter. A receiver exposed to the emitter is shown as a circle,
while a receiver screened from exposure to the emitter is shown as
a dot.
An orientation arrangement is needed to uniquely determine a
physical location because more than one location can produce the
same illumination pattern if the cart's orientation is changed. For
example, a two sensor system will produce the same pattern with the
mobile platform facing north or south, if the location is changed
to the opposite side of the emitter's centerline.
Another portion of FIG. 3 illustrates an array of receivers which
has three receivers 11 and a screen element 15 which, in a simple
vertical down looking view from above, appear to divide a circle
into three parts of one hundred twenty degrees rather than the two
one hundred eighty degrees semicircles of the two receiver
configuration. With three receivers and a trilateral screen
(illustrated in the lower portion of FIG. 3), the field of view of
each receiver is limited to approximately one sixth of a sphere.
The footprint of such an arrangement is also shown in FIG. 3.
FIGS. 4 and 5 show an array of receivers 11 where four receivers
are provided and the screen divides a circle into four quadrants of
ninety degrees. In such an arrangement, each receiver has its field
of view limited to approximately one eighth of a sphere and the
footprint appears as in FIG. 5. As is more clear from consideration
of these forms of the present invention in which more than two
receivers are shown, but as is also true of the simpler forms and
FIG. 3, the screening of the fields of view will result in the
fields of view of receivers overlapping to at least some
degree.
As mentioned above, position includes at least two
elements--location and orientation. The circuitry operatively
associated with the receivers can distinguish both characteristics
in one of several possible ways. One approach is to include in the
circuitry an orientation device such as a solid state compass or
device responsive to magnetic directions. Such a device would
enable an input indicative of orientation of the cart 10 relative
to the cardinal points of the compass. Another approach would use
the possible digital encoding of emitter signals and the
differentials in reception at the receivers to distinguish
orientation relative to a plurality of receivers, particularly
where the ceiling array is such that the array of receivers could
view and respond to a plurality of emitters at any given position.
In this instance, considering the footprint of, for example, a four
receiver array, one receiver might be illuminated by one emitter
(for example the receiver in the upper right quadrant of FIG. 5)
while another (for example the receiver in the lower left quadrant
of that array) is illuminated by a differently encoded emitter. The
associated circuitry could then distinguish between these patterns
to determine not only location but also orientation. As yet another
alternative, the circuitry could include an inertial device which
internally tracks movement of the cart.
In practice of methods in accordance with this invention, the
processes include mounting a plurality of radiation receivers on a
mobile platform; screening each of the receivers to limit the field
of receptivity thereof to a defined portion of a sphere;
distinguishing among a plurality of patterns of reception of
radiation at the receivers; and identifying a position of the
platform relative to the radiation sources based upon recognition
of the patterns of reception. More detailed steps possible are
believed to be clear from the apparatus discussion given above.
In the drawings and specifications there has been set forth a
preferred embodiment of the invention and, although specific terms
are used, the description thus given uses terminology in a generic
and descriptive sense only and not for purposes of limitation.
* * * * *